The present invention is directed to attachment systems for mounting cooling fans on motors, and particularly, automotive cooling system fans which are driven by electric motors.
Automotive cooling systems often employ cooling fans which are driven by electric motors. The fan must be physically attached to the motor in some manner. The cooling fan and motor system must be relatively compact, and ideally the axial length of the fan and motor assembly should be minimized, in order to be accommodated in the ever-decreasing design allocation space afforded under the hood of a modern automobile. Another imperative in the automotive industry is to reduce manufacturing costs through simplification of parts fabrication and assembly. In an effort to maximize fuel economy, it is also desirable to reduce weight of the fan and motor assembly wherever feasible.
There is also a need for high reliability in the cooling system and motor assembly, which is often exposed to rain and water splashing; sometimes in corrosive environments such as near sea shores. Consumer demand for vehicles which run quietly with minimal vibration requires that the combined fan and motor assembly operate with minimal noise and vibration; hence fan and motor dynamic running imbalance during operation and the life cycle of the components must be minimized.
As one skilled in the art can appreciate, minimization of size, weight, noise and vibration during the life cycle of the unit as well as manufacturing cost, with maximization of reliability often present conflicting design parameters, and ultimately design choices.
Previously known motor fan and cooling assemblies have attached the fan to the motor shaft by radial spring clips, similar to belleville washers, which provided axial tension to secure the fan to the shaft. The spring clip engaged the shaft in a groove formed in the shaft. Over the life cycle of the fan and motor, the spring clip could have fatigued and thereafter broken, which caused separation of the fan from the motor shaft. Addition of a spring clip securing attachment system to a fan and motor assembly inherently increased the axial length of the assembled structure. It is also noted that the spring clip did not readily inhibit a rocking of the fan relative to the motor shaft for two reasons: (a) the spring clip flexed in response to rocking loads on the fan, and (b) the relatively small diameter of the spring clip did not leave a very large bearing surface to counteract rocking loads on the fan.
Other known mounting attachment systems for cooling fans and motor shafts involved molding a metal hub within the fan. The metal hub was attached to the motor shaft via a pin, such as a roll pin. The molded-in-place hub and pin mounting system increased manufacturing complexity in a number of ways. First, the motor shaft was drilled to receive the pin. Second, plastic fans which included molded-in-place metal hubs were inherently more expensive to manufacture than fans which were only constructed of plastic. Third, the fan and motor assemblies which required insertion of pins added additional manufacturing assembly steps.
There has been a long-felt need in the automotive industry for a motor and cooling fan attachment system which reduced axial length of the assembly, reduced weight and manufacturing costs, increased reliability during the life cycle of the product and maintained good dynamic balance (hence lower vibration and noise) over the life cycle of the product, yet was relatively inexpensive to manufacture and assemble.